The present invention is directed toward improvements in an apparatus and method for the manufacture of reinforced elastomeric fabrics which are ultimately incorporated in a variety of goods including power drive belts, reinforced hose, containers such as fuel cells and, most particularly, in tires. With the exception of modern, cast elastomer technology, which does not require reinforcement, it has been well recognized that conventionally employed elastomeric stocks, e.g., rubber, do not possess the inherent strength either to maintain their integrity during the processing steps necessary to obtain the desired article or ultimately to function as an acceptable product when subjected to normal use. Thus, the elastomers have been reinforced as sheets, or layers of fabric, by the inclusion of embedded tibers, mono or polyfilament, which are considerably less extensible than the elastomer. These filaments, or reinforcing cords, include materials such as cotton, synthetics such as rayon, nylon and polyesters, fiberglass and metallic wire, particularly steel, either single strand or cabled.
Calendering has been the historic way in which to make reinforced elastomeric fabric, especially for tire plies; however, calendering requires expensive equipment and highly skilled operators to make the sheets of fabric, particularly in widths sufficient to provide a predetermined biased orientation of reinforcing filaments within the finished tire or other article.
When fabric is calendered the reinforcing cords are oriented parallel to the length of the fabric emanating from the calender. As such, in order for the reinforcing cords to be angularly inclined with respect to a circumferential reference plane when the fabric is incorporated in a tire, it is necessary to cut the fabric on the bias. Bias cutting, particularly when the angle desired demands a long cut, is a difficult process requiring expensive machinery and entails considerable waste.
In view of the cost of wire reinforcing, such waste is intolerably expensive and attempts have therefore been engendered to devise an apparatus for severing elemental strips from a continuous ribbon of wire reinforced material and assembling those elemental strips in adjacent juxtaposition so as to form a belt, or sheet, in which the reinforcing material is disposed at the desired bias.
Such attempts have largely centered upon feeding the ribbon past a cutting mechanism and onto an assembly table at a predetermined angle with respect to the cutting mechanism; severing a strip of predetermined length from the ribbon; and, manipulating the strip so as to stitch it to the preceding strip on the assembly table. Only after considerable experimentation was it discovered that the ribbon could not be satisfactorily fed past the cutting mechanism and onto the assembly table. In prior known devices the flexible nature of the ribbon has required considerable manipulation of the strip subsequent to the time it was severed from the ribbon in order to effect even a modicum of satisfactory stitching to the precedingly deposited strip. As such, apparatus embodying the "feeding" approach have become unduly complicated and the results too unpredictable for commercial acceptance.
One apparatus which has eliminated the need for calendering by the assembly of elemental strips severed from a continuous ribbon to form a reinforced fabric of desired width, has been described in U.S. Pat. No. 3,803,965, which patent is owned by our common assignee, The Steelastic Company. The apparatus and accompanying method by which it is operated have enjoyed commercial acceptance throughout the world for the production of reinforced fabric of varying widths, bias angles and carrying any of the known reinforcing filaments. The apparatus is particularly suitable for the manufacture of wire reinforced fabric, the wire comprising the commonly known, expensive steel cables or the wire helices described in U.S. Pat. No. 3,682,222, also owned by our common assignee.
In order to simplify the following disclosure, the aforementioned apparatus may be briefly summarized, including: an extruder through which the reinforcing filaments are drawn and encapsulated in an uncured, elastomeric compound, the composition of which is not necessarily important to the inventions described herein inasmuch as it will vary according to the desired uses of the resulting fabric; guide means for preliminarily orienting the reinforced ribbon, drawn from the extruder, on a lead-in table; a transfer means for positively engaging a portion of the ribbon on the lead-in table, metering a predetermined length thereof and withdrawing it; an assembly table upon which the metered, withdrawn length of ribbon is deposited by the transfer means; and, a guillotine means for severing the strip of predetermined length from the ribbon subsequent to its precise deposition upon the assembly table by the transfer means. A detailed description of the operation of this apparatus may be found in the aforementioned patent, U.S. Pat. No. 3,803,965, the subject matter of which is hereby incorporated by reference.
Notwithstanding the favorable operability of this apparatus, it has been found that the manufacture of relatively large widths, e.g., greater than two feet, of reinforced fabric, for uses such as body plies of radial truck tires, has necessitated some improvements to the basic apparatus. These improvements are of a nature that they have refined the operation of the basic apparatus irrespective of the width, thickness, bias angle or other parameters of the reinforced fabric being produced.
One of the problems has been the accurate deposition of larger strips of the reinforced ribbon. When it became desirable to construct wider fabrics, it became necessary to employ longer strips. Moreover, to increase the efficiency as well as the output of the apparatus, the width of each strip was increased inasmuch as an increase in the width of the strips resulted in a decrease in the number of strips necessary to form a reinforced fabric of any given length. It was thus found that movement of a larger transfer means to accommodate the greater dimensioned ribbons required more guidance and support than when the smaller strips were being transferred.
Another problem relates to the joining of the several elemental ribbons together to form the continuous fabric in a manner which provides a fabric which will not separate during subsequent fabrication operations. Still another problem relating to joining of the strips, resides in the precise indexing or forward incremental movement of the assembly table to facilitate the accurate deposition of each successively laid severed strip of ribbon.
A major problem is encountered when the severed incremental strips are indexed along the assembly mechanism at, or at approximately, 90.degree. with respect to the orientation of the ribbon on the table portion of the lead-in mechanism. This problem is further compounded when metallic reinforcing filaments are employed. In this situation, the action of the guillotine means, or vertically opposed knife blades, which sever each strip, occasionally results in a puckering of the last severed strip on the assembly table against the stationary lower knife blade. Frictional engagement therewith can retard advancement of that strip upon the assembly table sufficiently to cause malalignment thereof. Alternatively, the end of the severed strip, and particularly the metal reinforcing filaments therein, is in contiguous juxtaposition with the leading end of the continuous ribbon which impedes the free advancement of the strip during indexing of the assembly table again causing malalignment of the strip.
Obviously, separation of adjacent strips or the malalignment thereof from whatever cause is not conducive to the production of acceptable fabric or the trouble-free operation of the apparatus. Accurate positioning of successive strips upon the assembly table and the maintenance of that position during subsequent steps of fabric formation is thus essential and problems which would interfere with either are desirably to be eliminated.